The present invention pertains to valves that control fluid flow rate, and more specifically pertains to actuators for changing the fluid flow rate of the aforesaid valves.
Fluid flow control valves are generally known in the art. More specifically, U.S. Pat. Nos. 4,893,649, 5,143,116, and 5,234,025, all issued to Skoglund, generally disclose valves which provide a constant fluid flow despite upstream pressure fluctuations. Additionally, it is known in the art to alter the desired fluid flow rate through the valve by varying the fluid stream through the valve with a mechanism that requires hands-on adjustment. Thus, the prior art fluid flow control valves must be easily accessible if the fluid flow rate is to be varied.
However, valves which provide constant fluid flow rate are often necessarily employed in hostile or inaccessible environments such as, for example, in offshore, undersea oil drilling platforms, in nuclear reactors where a high level of radioactivity exists, in chemical plants where toxic chemicals are employed, and sealed in the walls, floors and/or ceilings of commercial and residential buildings.
Furthermore, the mechanical actuators known in the art, because they require hands-on adjustment, often do not provide the desired accuracy of fluid flow rate control. The only way to ensure the requisite accuracy of fluid flow rate control is to remove the requirement for humans to manually adjust the actuator mechanism.
A need thus exists for a fluid flow control valve having an actuator for changing fluid flow rate wherein the actuator can be remotely controlled from a distant location so that the valve can be employed in hazardous and inaccessible locations.
A need also exists for the above type of valve and actuator where the fluid flow rate control by the actuator is facilitated by pressurized fluid which causes movement of the actuator, thus providing a more accurate control of actuator movement than can be accomplished by manual adjustment.
A need further exists for the above type of valve and actuator where solenoid valves control the passage of fluid into the actuator and the passage of fluid out of the actuator, and wherein the solenoid valves are remotely controlled.
An additional need exists for the above type of valve and actuator where a differential pressure transducer communicates with a plurality of locations within the valve to monitor pressure differences within the valve.
A need also exists for a valve and actuator wherein the actuator is spring-biased, and the springs have a preload bias equivalent to the ambient pressure of the actuator fluid such that the actuator can function in high pressure environments with which the actuator fluid is in equilibrium.